CN110556853B - Calculation method and system for providing initial value for electromagnetic transient simulation - Google Patents
Calculation method and system for providing initial value for electromagnetic transient simulation Download PDFInfo
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Abstract
The invention provides a calculation method and a system for providing an initial value for electromagnetic transient simulation, wherein first iteration load flow calculation is carried out based on acquired direct current power transmission system element parameters; correcting the per-unit transformation ratio of the transformation flow based on the first iteration load flow calculation result, and then performing second iteration load flow calculation; and determining the conduction state of each converter valve arm when the alternating current-direct current transmission system initially operates according to the second iteration load flow calculation result. The technical scheme provided by the invention provides an initial value which is accurate enough for the electromagnetic transient simulation of the alternating current-direct current hybrid power grid, so that the starting process of electromagnetic transient calculation is more stable, and the result is more accurate; the position of a tap joint of the converter transformer is adjusted to correct the transformation ratio and control different variables, so that the calculation result is closer to an actual system, and the initial values of the state variables of all elements in the direct current are further solved on the basis of the electromagnetic transient load flow result.
Description
Technical Field
The invention belongs to the field of power systems, and particularly relates to a calculation method and a system for providing an initial value for electromagnetic transient simulation.
Background
There are two operating states of the power system, namely steady state and transient state. When the system is in a steady state, the operation parameters including power, voltage, current, frequency, angular displacement between electromotive phasors and the like continuously change slightly around a certain average value, the operation parameters can be regarded as constants in analysis, and people usually analyze the steady-state process through load flow calculation; when the system is disturbed suddenly during operation, the operation parameters can change greatly, and the process can be divided into an electromechanical transient process caused by unbalance of mechanical torque and electromagnetic torque and an electromagnetic transient process of rapid change of current and voltage in elements such as circuits and transformers, and people usually analyze the latter process through electromagnetic transient simulation.
The electromagnetic transient simulation meter takes account of the rapid current and voltage change process, so the electromagnetic transient simulation meter has the characteristics of small simulation step length, complex simulation model and the like. System components generally need detailed modeling, and the level of detail depends on the needs, so most electromagnetic transient simulation software allows users to build models independently, typically for high-voltage direct-current transmission circuits. Taking a direct current model of an all-Digital Power System Simulator (ADPSS) of a Power System as an example, a direct current primary circuit is built by a large number of basic elements according to actual direct current engineering. The basic elements comprise three-phase RLC elements, single-phase RLC elements, thyristor elements, power transmission line elements, three-phase/single-phase fault elements, three-phase two-winding transformer elements and the like, and the number of nodes of a single-circuit direct-current power transmission model is more than 500.
Electromagnetic transient simulation generally establishes its own steady-state process on the basis of initial steady-state values. When a pure alternating current system is simulated, the system only comprises conventional fixed elements, and usually, load flow calculation can conveniently provide an initial value for electromagnetic transient simulation; however, when processing the aforementioned high-voltage direct-current model, because a large number of internal nodes of the model, a large number of power electronic components and a plurality of small branches are involved, conventional power flow calculation is difficult to provide initial values, and the related state quantities of the components are difficult to accurately define, so that disturbance is introduced due to imbalance of the initial values.
Disclosure of Invention
In order to solve the above problems in the prior art, the present invention provides a method and a system for providing an initial value for electromagnetic transient simulation.
A method for determining an electromagnetic transient simulation initial value of an alternating current-direct current hybrid power grid comprises the following steps:
performing first iteration load flow calculation based on the acquired direct current transmission system element parameters;
correcting the per-unit transformation ratio of the transformation flow based on the first iteration load flow calculation result, and then performing second iteration load flow calculation;
and determining the conduction state of each converter valve arm when the alternating current-direct current transmission system initially runs according to the second iteration load flow calculation result.
Preferably, the performing of the first iterative power flow calculation based on the obtained element parameters of the direct current transmission system includes: calculating direct current power according to the obtained alternating current-direct current division point bus and direct current system parameters;
bringing the direct-current power into an alternating-current network to perform iterative load flow calculation to obtain the voltage of a bus at an alternating-current and direct-current division point, and obtaining the per-unit transformation ratio of the converter transformer when the load flow is converged;
preferably, the direct-current power is brought into the alternating-current network to perform iterative computation to obtain the voltage of the alternating-current/direct-current division point bus, and the per-unit transformation ratio of the transformation current is corrected according to the voltage of the alternating-current/direct-current division point bus until the power flow is converged; as shown in the following formula:
n id ＝U' o1 /U o2r /K
wherein n is id The per unit transformation ratio of the rectifier side converter transformer is corrected; u' o1 Calculating the actual tap voltage for the first iteration load flow; u shape o2r Rating the voltage for the converter transformer valve side; k is the number of single-station unipolar six-pulse converters corresponding to the direct-current engineering;
actual tap voltage U 'after first iteration power flow calculation' o1 Calculated as follows:
U' o1 ＝U o1r +(Tap pos -Tap posr )*Tap step
wherein, U o1r A nominal voltage corresponding to a tap position in the nominal tap information; tap pos And Tap posr Respectively the current tap position and the main tap position of the converter transformer; tap step For the division of the tap adjustment, it is calculated as follows:
wherein, U o1 For the converter transformer primary side tap voltage, the following formula is calculated:
U o1 ＝n i U o2r K
wherein n is i Per unit transformation ratio of the converter transformer in iterative calculation; u shape o2r Rated voltage for the converter transformer valve side;
preferably, the correcting the per-unit transformation ratio of the transformation flow based on the first iterative power flow calculation result, and then performing the second iterative power flow calculation includes:
calculating direct-current power based on the corrected per-unit transformation ratio, the alternating-current and direct-current division point bus voltage and the direct-current coefficient parameters;
injecting the direct current power into an alternating current network, solving alternating current power flow, and obtaining an improved value of the bus voltage of the alternating current-direct current division point;
and judging whether the alternating current power flow is converged, and if not, repeating the two steps until the alternating current power flow is converged. And determining the per-unit conversion ratio of the stream, and determining the position of the variational joint according to the per-unit conversion ratio of the stream.
Preferably, determining the conduction state of each converter valve arm when the alternating current-direct current transmission system initially operates according to the second iteration load flow calculation result includes:
obtaining the per-unit transformation ratio of the transformation current, the direct current trigger angle, the direct current voltage and the state information of the direct current according to the second iteration load flow calculation result;
calculating the phase angle of the voltage eac at the AC side of the converter according to the connection method of the converter transformer;
and determining the conduction state of each converter valve arm in the initial direct current operation according to the phase angle of the alternating current side voltage eac of the converter, the trigger lag angle of the rectifier, the trigger lead angle of the inverter and the connection method of the converter transformer.
Preferably, the calculating the phase angle of the ac side voltage eac of the converter according to the connection method of the converter transformer includes:
when the connection method of the converter transformer is Y-delta-1, the line voltage phase angle of the network side of the converter transformer is calculated according to the following formula:
θ＝A*180°/π-60°；
when the connection method of the converter transformer is Y-Y-0, the voltage phase angle of the network side line of the converter transformer is calculated according to the following formula
θ＝A*180°/π-30°；
Wherein, theta is a phase angle of the alternating-current side voltage eac of the converter; a is the voltage phase angle of the converter transformer network side line;
preferably, the conduction state of each converter valve arm in the initial direct current operation is determined according to the phase angle of the ac side voltage eac of the converter, the rectifier triggering lag angle and the inverter triggering lag angle, and the rectifier triggering lag angle is calculated according to the following formula:
α＝ang0(ii)*180°/π
where α is the rectifier trigger lag angle, and ang0 (ii) is the initial value of the rectifier ii trigger lag angle;
the inverter trigger advance angle is calculated according to the following formula:
β＝ang0'(ii)*180./π
where β is an inverter over-firing angle, and ang0' (ii) is an initial value of the inverter ii over-firing angle.
Preferably, determining the conduction state of each converter valve arm in the initial direct current operation according to the phase angle of the alternating-current side voltage eac of the converter, the trigger lag angle of the rectifier, the trigger lead angle of the inverter and the connection method of the converter transformer, includes:
if α -150 ° < θ ≦ α -90 °, S (ii) = [0, 1];
if α -90 ° < θ ≦ α -30 °, S (ii) = [1,0, 1];
if α -30 ° < θ ≦ α +30 °, S (ii) = [1, 0];
if α +30 ° < θ ≦ α +90 °, S (ii) = [0,1, 0];
if 0 ° < α ≦ 30 ° and α +90 ° < θ ≦ α +150 °, S (ii) = [0,1, 0];
if 30 ° < α <90 ° and α +90 ° < θ ≦ 180 °, S (ii) = [0,1, 0];
if 30 ° < α <90 ° and-180 ° < θ ≦ α -210 °, S (ii) = [0,1, 0];
if 0 ° < α <30 ° and-180 ° < θ ≦ α -150 °, S (ii) = [0,1, 0];
if 0 ° < α <30 ° and α +150 ° < θ ≦ 180 °, S (ii) = [0,1, 0];
if 30 ° < α <90 ° and α -210 ° < θ ≦ α -150 °, S (ii) = [0,1, 0];
if 90-beta < theta.ltoreq.150-beta, S (ii) = [1,0, 1];
if 30-beta < theta.ltoreq.90-beta, S (ii) = [0, 1];
if-30 ° - β < θ ≦ 30 ° - β, then S (ii) = [0,1, 0];
if-90 ° - β < θ ≦ -30 ° - β, then S (ii) = [0,1, 0];
s (ii) = [0,1, 0] if 0 ° < β ≦ 30 ° and-150 ° - β < θ ≦ -90 ° - β;
s (ii) = [0,1, 0] if 30 ° < β <90 ° and-180 ° < θ ≦ -90 ° - β;
s (ii) = [0,1, 0] if 30 ° < β <90 ° and 210 ° - β < θ ≦ 180 °;
s (ii) = [1, 0] if 0 ° < β <30 ° and-180 ° < θ ≦ -150 ° - β;
s (ii) = [1, 0] if 0 ° < β <30 ° and 150 ° < β < θ ≦ 180 °;
if beta is more than or equal to 30 degrees and less than 90 degrees and 150 degrees to beta is more than or equal to 150 degrees and less than or equal to 210 degrees and beta, S (ii) = [1, 0];
s (ii) is a switching vector of the conduction state of each converter valve arm when the direct-current transmission system initially operates; alpha is a trigger lag angle; beta is a trigger crossing angle; theta is the phase angle of the AC side voltage of the converter.
Preferably, the method further comprises the following steps:
and according to the per-unit transformation ratio of the converter transformer, the direct-current trigger angle, the direct-current voltage, the state information of the direct current and the conduction state of each converter valve arm during the initial operation of the direct current, enabling the direct current circuit to be equivalent to a small-resistance circuit, and completing the initialization of the direct current circuit.
A system for determining an initial electromagnetic transient simulation value of an alternating current-direct current hybrid power grid comprises:
the first calculation module is used for performing first iteration load flow calculation based on the acquired direct current transmission system element parameters;
the second calculation module is used for correcting the per unit transformation ratio of the transformation flow based on the first iteration flow calculation result and then performing second iteration flow calculation;
and the control module is used for determining the conduction state of each converter valve arm when the alternating current-direct current transmission system initially operates according to the second iteration load flow calculation result.
Preferably, the first calculating module includes:
the power calculation submodule is used for calculating direct-current power according to the obtained alternating-current and direct-current division point bus and the direct-current system parameters;
and the converter transformer per unit transformation ratio calculation submodule is used for bringing the direct-current power into the alternating-current network to carry out iterative power flow calculation to obtain the voltage of the alternating-current and direct-current division point bus until power flow is converged, and obtaining the converter transformer per unit transformation ratio.
Preferably, the per-unit transformation ratio of the transformation stream is calculated according to the following formula:
n id ＝U' o1 /U o2r /K
wherein n is id The per unit transformation ratio of the rectified rectifier side converter transformer is corrected; u' o1 Actual tap voltage after the first iteration load flow calculation is carried out; u shape o2r Rated voltage for the converter transformer valve side; k is the number of single-station unipolar six-pulse converters corresponding to the direct-current engineering;
actual tap voltage U 'after first iteration power flow calculation' o1 Calculated as follows:
U' o1 ＝U o1r +(Tap pos -Tap posr )*Tap step
wherein, U o1r A nominal voltage corresponding to a tap position in the nominal tap information; tap pos And Tap posr Respectively the current tap position and the main tap position of the converter transformer; tap step For the division of the tap adjustment, the following is calculated:
wherein, U o1 For changing the currentThe variable primary side tap voltage is calculated according to the following formula:
U o1 ＝n i U o2r K
wherein n is i The per-unit transformation ratio of the converter transformer in iterative calculation is calculated; u shape o2r Rated voltage for the converter transformer valve side;
preferably, the second calculation module includes:
the direct current power calculation submodule: the DC power calculating unit is used for calculating DC power based on the corrected per unit transformation ratio, the AC/DC division point bus voltage and the DC coefficient parameter;
the load flow alternating current calculation submodule comprises: the direct current power is injected into an alternating current network, alternating current power flow is solved, and an improved value of the bus voltage of the alternating current-direct current division point is obtained;
a judgment submodule: and the step of judging whether the alternating current power flow is converged, and if not, repeating the two steps until the alternating current power flow is converged.
Compared with the closest prior art, the technical scheme provided by the invention has the following beneficial effects:
according to the technical scheme provided by the invention, the first iteration load flow calculation is carried out based on the obtained element parameters of the direct current power transmission system; correcting the per-unit transformation ratio of the transformation flow based on the first iteration load flow calculation result, and then performing second iteration load flow calculation; and determining the conduction state of each converter valve arm when the alternating current-direct current transmission system initially operates according to the second iteration load flow calculation result. The method provides an initial value with sufficient accuracy for the electromagnetic transient simulation of the alternating-current and direct-current hybrid power grid, so that the starting process of electromagnetic transient calculation is more stable, and the result is more accurate.
The technical scheme provided by the invention corrects the transformation ratio and controls different variables by adjusting the position of the tap joint of the converter transformer, so that the calculation result is closer to an actual system, and the initial values of the state variables of all elements in the direct current are further solved on the basis of the electromagnetic transient load flow result.
Drawings
FIG. 1 is a flow chart of a method for determining an initial value of electromagnetic transient simulation of an AC/DC hybrid power grid according to the invention;
FIG. 2 is a schematic diagram of an AC/DC hybrid power grid according to the present invention;
FIG. 3 is a flowchart of an electromagnetic transient power flow calculation according to the present invention;
FIG. 4 is a flow chart of the present invention for determining the initial conduction state of each valve.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings. In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.
Example 1
Fig. 2 is a schematic diagram of an ac/dc hybrid power grid according to the present invention, the ac/dc hybrid power grid can be divided into two parts, i.e., dc and ac, and a node i and a node j are division points of an ac/dc system. The direct current power (the power on the converter transformer network side) is regarded as a power injection source of an alternating current system, and the alternating current filter is regarded as a common RLC (radio link control) element and is included in an alternating current network. The whole load flow calculation adopts a three-phase Newton method, and each iteration step is carried out according to the sequence of firstly calculating direct current power and then calculating alternating current load flow. The solving steps of the alternating current-direct current hybrid power grid are described as follows:
(1) Assuming that the converter transformer tap can be adjusted at will within the upper and lower limits, the AC/DC split point bus voltage U of the i node and the j node is known i 、U j And calculating the direct current self power P of the i node and the j node according to the direct current system parameters i +jQ i 、P j +jQ j Calculating the per-unit transformation ratio n of the converter transformer at the i node and the j node of the converter transformer i And n j ；
(2) Injecting the obtained direct current power into an alternating current network, solving the alternating current power flow to obtain the alternating current-direct current division point bus voltage U of the i node and the j node i 、U j The improvement value of (c);
(3) Repeating the two steps until the alternating current power flow is converged;
(4) Correcting per unit transformation ratio n of converter transformer i node according to converter transformer tap information i And the per unit transformation ratio n of the j node j ；
(5) Fixing the converter transformer joint according to the AC/DC division point bus voltage U i 、U j And calculating the direct current self power P of the i node according to the direct current system parameters i +jQ i And the direct current self power P of the j node j +jQ j Calculating the trigger angle alpha and the DC voltage V on the rectifying side di Etc.;
(6) Injecting the obtained direct current power into an alternating current network, solving the alternating current power flow to obtain the alternating current-direct current division point bus voltage U of the i node and the j node i 、U j The improvement value of (c);
(7) Repeating the above two steps until the AC power flow is converged
The solution process of the alternating current part is the same as that of the conventional power flow calculation, and the description is omitted here. The control mode of direct current is different, and the known quantity and the unknown quantity during direct current calculation are influenced, the formula is slightly different, but the algorithm is not essentially different. Therefore, the following description will be given only by taking the most common rectification-side constant current and inverter-side constant arc-extinguishing angle control method as an example.
The method for determining the initial value of the electromagnetic transient simulation of the ac-dc hybrid power grid is further described below with reference to fig. 1 and 3:
the method comprises the following steps: performing first iteration load flow calculation based on acquired direct current transmission system element parameters
Known as R dc 、X ci 、X cj 、I d 、V di 、γ 0 、α 0 And an AC node voltage U i 、U j Obtaining the per-unit transformation ratio n of the i node of the converter transformer through the ideal no-load direct-current voltage of the rectifying side without phase control i And the per unit transformation ratio n of the j node j And injection current I of AC node I i And the injection current I of the AC node j j ；
The calculation formula of the ideal no-load direct-current voltage of the rectification side without phase control is as follows:
wherein, V di For rectifying side direct currentA voltage given value; x is a radical of a fluorine atom ci Is the leakage reactance of the converter transformer at node i; I.C. A d Setting a direct current value; alpha (alpha) ("alpha") 0 Setting operating values for a trigger angle of a rectification side;
converter transformer i node per unit transformation ratio n i The calculation formula is as follows:
n i ＝U i /(V oi /N)
wherein n is i The per unit transformation ratio of the converter transformer of the i node in the first iteration is obtained; u shape i Is the voltage of the ac node I; v dj The value is the DC voltage value of the inversion side; n is the number of operating poles of the direct current system;
I i ＝I d /n i
wherein, I i The injection current of the alternating current node I in the first iteration;
V dj ＝V di -I d R dc
wherein, V dj The value of the direct current voltage of the inversion side in the first iteration is obtained; r dc Is the loop resistance of the direct current system;
wherein, V oj The ideal no-load direct-current voltage of the inversion side in the first iteration is subjected to phase-free control; x is the number of cj Is the leakage reactance of the converter transformer at node J; gamma ray 0 Setting the operation value of an inversion arc extinguishing angle;
n j ＝U j /(V oj /N)
wherein n is j The per-unit transformation ratio of the converter transformer at the node J in the first iteration is obtained; u shape j Is the voltage of the ac node J in the first iteration;
I j ＝I d /n j
wherein, I i The injection current at the alternating current node I in the first iteration is obtained; n is a radical of an alkyl radical j The per unit transformation ratio of the converter transformer of the J node in the first iteration is obtained;
wherein,
is a DC rectification side power factor angle;
wherein,
is a DC inversion side power factor angle;
P i ＝-U i I i cosφ i
Q i ＝-U i I i sinφ i
P j ＝U j I j cosφ j
Q j ＝-U j I j sinφ j
the rectification side converter tap adjustment will be described as an example.
After the first iteration, the primary side tap voltage of the converter transformer is calculated according to the following formula:
U o1 ＝n i U o2r K
wherein, U o2r Rated voltage for the converter transformer valve side; k is the number of single-station unipolar six-pulse current converters corresponding to the direct-current engineering;
the actual position of the tap is determined according to the following formula:
wherein, U o1r A nominal voltage corresponding to a tap position in the nominal tap information; tap pos And Tap posr Respectively the current tap position and the main tap position of the converter transformerPlacing; tap step Indexing for tap adjustment;
the actual tap voltage can thus be found to be:
U' o1 ＝U o1r +(Tap pos -Tap posr )*Tap step
wherein, U' o1 For the actual tap voltage after the first iteration load flow calculation
The corrected conversion transformer per unit transformation ratio is as follows:
n id ＝U' o1 /U o2r /K
step two: correcting the per unit transformation ratio of the transformation flow based on the first iteration load flow calculation result, and then performing the second iteration load flow calculation
Known as R dc 、X ci 、X cj 、n id 、n jd 、I d 、γ 0 And an AC node voltage U i 、U j To find alpha 0 、V' di 、I' i 、I' j The calculation formula is as follows:
I' j ＝I d /n jd
wherein, I' j Is the injected current at the ac node J in the second iteration;
V' oj ＝(V j /n jd )×N
wherein, V' oj The ideal no-load direct current voltage of the inversion side in the second iteration is phase-free controlled;
wherein, V' dj The value of the direct current voltage at the inversion side in the second iteration is obtained;
V' di ＝V' dj +I d R dc
wherein, V' di The direct current voltage value of the rectification side in the second iteration is obtained;
V' oi ＝(V i /n id )×N
wherein, V' oi Is the second stackThe neutral rectification side is used for replacing the phase-free ideal no-load direct-current voltage;
I' i ＝I d /n id
wherein, I' i The injected current of the alternating current node i in the second iteration;
P i ＝-U i I i cosφ i
Q i ＝-U i I i sinφ i
P j ＝U j I j cosφ j
Q j ＝-U j I j sinφ j
the determination of the conduction state of each converter valve arm in the initial operation of the ac-dc transmission system according to the second iteration load flow calculation result will be further described with reference to fig. 4
Step three: and determining the conduction state of each converter valve arm when the alternating current-direct current transmission system initially runs according to the second iteration load flow calculation result.
After the electromagnetic transient load flow calculation is completed, state information such as a converter transformer tap, a direct current trigger angle, direct current voltage, direct current and the like is obtained, and the initialization of the whole direct current circuit can be completed only by determining the initial conduction state of each converter valve arm to be equivalent to a small-resistance branch circuit. The invention provides a method for reasonably determining the initial conduction state of each converter valve arm, which is described as follows.
By reading the above tidal current results, the voltage phase angle of the converter transformer network side, the triggering lag angle of the rectifier valve and the triggering advance angle of the inverter valve are known. The related parameter conventions are as follows:
ii converter serial number.
A: the voltage phase angle (degree) of the grid side line of the converter transformer.
CTCONNECT: and connecting the converter transformer. CTCONNECT (i) represents the ith converter transformer connection, and when the value is 0, the value represents the Y-delta-1 connection, and when the value is 1, the Y-Y-0 connection is represented.
ANG0: the converter trigger lag angle (trigger lead angle) is the initial value (degree).
S: and switching vectors of the conduction states of the converter valve arms. S (i, j) represents the on state of the jth valve of the ith converter, a value of 0 indicates that the valve is in the off state, and a value of 1 indicates that the valve is in the on state.
The method for determining the conducting state of each valve wall of the ii-th converter comprises the following steps:
(1) Calculating the phase angle of the AC side voltage eac of the converter, wherein when CTCONNECT (ii) =1, theta = A180 DEG/pi-30 DEG, and when CTCONNECT (ii) =0, theta = A180 DEG/pi-60 DEG
(2) Rectification side valve wall conducting state switch vector S
Trigger lag angle α = ang0 (ii) × 180 °/π
If α -150 ° < θ ≦ α -90 °, S (ii) = [0, 1]
If α -90 ° < θ ≦ α -30 °, S (ii) = [1,0, 1]
If α -30 ° < θ ≦ α +30 °, S (ii) = [1, 0]
If α +30 ° < θ ≦ α +90 °, S (ii) = [0,1, 0]
If (0 ° < α ≦ 30 ° and α +90 ° < θ ≦ α +150 °) or (30 ° < α <90 ° and (α +90 ° < θ ≦ 180 ° or-180 ° < θ ≦ α -210 °), S (ii) = [0,1, 0]
If (0 ° < α <30 ° and (-180 ° < θ ≦ α -150 ° or α +150 ° < θ ≦ 180 °)) or (30 ° < α <90 ° and α -210 ° < θ ≦ α -150 °), S (ii) = [0,1, 0]
(3) Inverter side valve wall conduction state switch vector S
Trigger crossing angle β = ang0 (ii) · 180./π
If 90-beta < theta.ltoreq.150-beta, S (ii) = [1,0, 1]
If 30-beta < theta.ltoreq.90-beta, S (ii) = [0, 1]
If-30-beta < theta.ltoreq.30-beta, S (ii) = [0,1, 0]
If-90-beta < theta > is less than or equal to-30-beta, then S (ii) = [0,1, 0]
If (0 ° < β ≦ 30 ° and-150 ° < θ ≦ -90 ° - β) or (30 ° < β <90 ° and (-180 ° < θ ≦ -90 ° - β or 210 ° < β ≦ 180 °), S (ii) = [0,1, 0]
If (0 ° < beta <30 ° and (-180 ° < theta.ltoreq-150 ° -beta or 150 ° -beta < theta.ltoreq.180 °)) or (30 ° < beta <90 ° and 150 ° -beta < theta.ltoreq.210 ° -beta), S (ii) = [1, 0]
The calculation method further comprises the following steps:
and according to the per-unit transformation ratio of the converter transformer, the direct-current trigger angle, the direct-current voltage, the state information of the direct current and the conduction state of each converter valve arm during the initial operation of the direct current, enabling the direct current circuit to be equivalent to a small-resistance circuit, and completing the initialization of the direct current circuit.
Example 2:
based on the same invention concept, the invention also provides a system for determining the electromagnetic transient simulation initial value of the alternating current-direct current hybrid power grid, which comprises the following steps:
the first calculation module is used for performing first iteration power flow calculation based on the acquired direct current transmission system element parameters;
the second calculation module is used for correcting the per-unit transformation ratio of the transformation flow based on the first iteration load flow calculation result and then performing second iteration load flow calculation;
and the control module is used for determining the conduction state of each converter valve arm when the alternating current-direct current transmission system initially operates according to the second iteration load flow calculation result.
The first computing module comprises:
the power calculation submodule is used for calculating direct-current power according to the obtained alternating-current and direct-current division point bus and the direct-current system parameters;
and the converter transformer per unit transformation ratio calculation submodule is used for bringing the direct-current power into the alternating-current network to carry out iterative power flow calculation to obtain the voltage of the alternating-current and direct-current division point bus until power flow is converged, and obtaining the converter transformer per unit transformation ratio.
The per-unit transformation ratio of the transformation flow is calculated according to the following formula:
n id ＝U' o1 /U o2r /K
wherein n is id The per unit transformation ratio of the rectifier side converter transformer is corrected; u' o1 Calculating the actual tap voltage for the first iteration load flow; u shape o2r Rating the voltage for the converter transformer valve side; k is the number of single-station unipolar six-pulse current converters corresponding to the direct-current engineering;
actual tap voltage U 'after first iteration power flow calculation' o1 Calculated as follows:
U' o1 ＝U o1r +(Tap pos -Tap posr )*Tap step
wherein, U o1r A nominal voltage corresponding to a tap position in the nominal tap information; tap pos And Tap posr Respectively the current tap position and the main tap position of the converter transformer; tap step For the division of the tap adjustment, the following is calculated:
wherein, U o1 For the converter transformer primary side tap voltage, the following formula is calculated:
U o1 ＝n i U o2r K
wherein n is i The per-unit transformation ratio of the converter transformer in iterative calculation is calculated; u shape o2r Rating the voltage for the converter transformer valve side;
the second calculation module includes:
the direct current power calculation submodule: the DC power calculating unit is used for calculating DC power based on the corrected per unit transformation ratio, the AC/DC division point bus voltage and the DC coefficient parameter;
the load flow alternating current calculation submodule comprises: the direct current power is injected into an alternating current network, and alternating current power flow is solved to obtain an improved value of the bus voltage of the alternating current-direct current division point;
a judgment submodule: and the step of judging whether the alternating current power flow is converged, and if not, repeating the two steps until the alternating current power flow is converged.
The control module includes:
a per unit transformation ratio determining sub-module: the current-to-unit transformation ratio is determined according to the second iteration load flow calculation result;
and (3) a sub-module is determined by a connection method: the tap position is determined according to the per-unit conversion ratio of the converter transformer, and then the connection method of the converter transformer is determined;
the phase angle calculation submodule: the phase angle of the voltage eac at the AC side of the converter is calculated according to the connection method of the converter transformer;
the valve arm conduction state determination submodule: and the converter valve arm conduction state during the initial direct current running is determined according to the phase angle of the alternating current side voltage eac of the converter, the trigger lag angle of the rectifier and the trigger lead angle of the inverter.
The phase angle of the alternating-current side voltage eac of the converter is calculated according to the following formula:
when the connection method of the converter transformer is Y-delta-1, the voltage phase angle of the network side line of the converter transformer is calculated according to the following formula:
θ＝A*180°/π-60°；
when the connection method of the converter transformer is Y-Y-0, the line voltage phase angle of the network side of the converter transformer is calculated according to the following formula, wherein theta = A x 180 °/pi-30 °;
wherein, theta is a phase angle of the alternating-current side voltage eac of the converter; a is the voltage phase angle of the side line of the converter transformer network. The rectifier trigger lag angle and the inverter trigger lead angle are calculated according to the following formula
The trigger lag angle of the rectifier is calculated according to the following formula:
α＝ang0(ii)*180°/π
where α is the rectifier trigger lag angle, and ang0 (ii) is the initial value of the rectifier trigger lag angle;
the inverter trigger advance angle is calculated according to the following formula:
β＝ang0'(ii)*180./π
where β is the inverter trigger advance angle, and ang0' (ii) is the initial value of the inverter ii trigger advance angle. The valve arm conduction state determining submodule is used for judging according to the following formula:
if α -150 ° < θ ≦ α -90 °, S (ii) = [0, 1];
if α -90 ° < θ ≦ α -30 °, S (ii) = [1,0, 1];
if α -30 ° < θ ≦ α +30 °, S (ii) = [1, 0];
if α +30 ° < θ ≦ α +90 °, S (ii) = [0,1, 0];
if 0 ° < α ≦ 30 ° and α +90 ° < θ ≦ α +150 °, S (ii) = [0,1, 0];
if 30 ° < α <90 ° and α +90 ° < θ ≦ 180 °, S (ii) = [0,1, 0];
if 30 ° < α <90 ° and-180 ° < θ ≦ α -210 °, S (ii) = [0,1, 0];
if 0 ° < α <30 ° and-180 ° < θ ≦ α -150 °, S (ii) = [0,1, 0];
if 0 ° < α <30 ° and α +150 ° < θ ≦ 180 °, S (ii) = [0,1, 0];
if 30 ° < α <90 ° and α -210 ° < θ ≦ α -150 °, S (ii) = [0,1, 0];
if 90-beta < theta.ltoreq.150-beta, S (ii) = [1,0, 1];
if 30-beta < theta.ltoreq.90-beta, S (ii) = [0, 1];
if-30 ° - β < θ ≦ 30 ° - β, then S (ii) = [0,1, 0];
if-90 ° - β < θ ≦ -30 ° - β, then S (ii) = [0,1, 0];
s (ii) = [0,1, 0] if 0 ° < β ≦ 30 ° and-150 ° - β < θ ≦ -90 ° - β;
s (ii) = [0,1, 0] if 30 ° < β <90 ° and-180 ° < θ ≦ -90 ° - β;
s (ii) = [0,1, 0] if 30 ° < β <90 ° and 210 ° - β < θ ≦ 180 °;
s (ii) = [1, 0] if 0 ° < β <30 ° and-180 ° < θ ≦ -150 ° - β;
s (ii) = [1, 0] if 0 ° < β <30 ° and 150 ° < β < θ ≦ 180 °;
if beta is more than or equal to 30 degrees and less than 90 degrees and 150 degrees to beta is more than or equal to 150 degrees and less than or equal to 210 degrees and beta, S (ii) = [1, 0];
s (ii) is a switching vector of the conduction state of each converter valve arm when the direct-current transmission system initially operates; alpha is a trigger lag angle; beta is the trigger advance angle; theta is the phase angle of the ac side voltage of the inverter.
The computing system, further comprising:
and the application module is used for equating the direct current circuit into a small-resistance circuit according to the per unit transformation ratio of the converter transformer, the direct current trigger angle, the direct current voltage, the state information of the direct current and the conduction state of each converter valve arm during the initial operation of the direct current, and finishing the initialization of the direct current circuit.
It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and so forth) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The present invention is not limited to the above embodiments, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention are included in the scope of the claims of the present invention as filed.
Claims (11)
1. A method of providing an initial value for electromagnetic transient simulation, comprising:
performing first iteration load flow calculation based on the acquired direct current transmission system element parameters;
correcting the per-unit transformation ratio of the transformation flow based on the first iteration load flow calculation result, and then performing second iteration load flow calculation;
determining the conduction state of each converter valve arm when the alternating current-direct current transmission system initially operates according to the second iteration load flow calculation result;
determining the conduction state of each converter valve arm when the alternating current-direct current transmission system initially operates according to the second iteration load flow calculation result, wherein the method comprises the following steps:
obtaining the per-unit transformation ratio of the transformation current, the direct current trigger angle, the direct current voltage and the state information of the direct current according to the second iteration load flow calculation result;
calculating the phase angle of the voltage eac at the AC side of the converter according to the connection method of the converter transformer;
determining the conduction state of each converter valve arm in the initial direct current operation according to the phase angle of the alternating current side voltage eac of the converter, the trigger lag angle of the rectifier, the trigger lead angle of the inverter and the connection method of the converter transformer;
the determining the conduction state of each converter valve arm in the initial direct current operation according to the phase angle of the alternating current side voltage eac of the converter, the trigger lag angle of the rectifier, the trigger lead angle of the inverter and the connection method of the converter transformer comprises the following steps:
if α -150 ° < θ ≦ α -90 °, S (ii) = [0, 1];
if α -90 ° < θ ≦ α -30 °, S (ii) = [1,0, 1];
if α -30 ° < θ ≦ α +30 °, S (ii) = [1, 0];
if α +30 ° < θ ≦ α +90 °, S (ii) = [0,1, 0];
if 0 ° < α ≦ 30 ° and α +90 ° < θ ≦ α +150 °, S (ii) = [0,1, 0];
if 30 ° < α <90 ° and α +90 ° < θ ≦ 180 °, S (ii) = [0,1, 0];
if 30 ° < α <90 ° and-180 ° < θ ≦ α -210 °, S (ii) = [0,1, 0];
if 0 ° < α <30 ° and-180 ° < θ ≦ α -150 °, S (ii) = [0,1, 0];
if 0 ° < α <30 ° and α +150 ° < θ ≦ 180 °, S (ii) = [0,1, 0];
if 30 ° < α <90 ° and α -210 ° < θ ≦ α -150 °, S (ii) = [0,1, 0];
if 90-beta < theta.ltoreq.150-beta, S (ii) = [1,0, 1];
if 30 ° - β < θ ≦ 90 ° - β, then S (ii) = [0, 1];
if-30 ° - β < θ ≦ 30 ° - β, S (ii) = [0,1, 0];
if-90 ° - β < θ ≦ -30 ° - β, then S (ii) = [0,1, 0];
s (ii) = [0,1, 0] if 0 ° < β ≦ 30 ° and-150 ° - β < θ ≦ -90 ° - β;
s (ii) = [0,1, 0] if 30 ° < β <90 ° and-180 ° < θ ≦ -90 ° - β;
s (ii) = [0,1, 0] if 30 ° < β <90 ° and 210 ° - β < θ ≦ 180 °;
s (ii) = [1, 0] if 0 ° < β <30 ° and-180 ° < θ ≦ -150 ° - β;
s (ii) = [1, 0] if 0 ° < β <30 ° and 150 ° < β < θ ≦ 180 °;
(iii) S (ii) = [1, 0] if 30 ° < β <90 ° and 150 ° < β < θ < 210 ° - β;
s (ii) is a switching vector of the conducting state of each converter valve arm when the direct current transmission system initially operates; alpha is the trigger lag angle of the rectifier; beta is an over-front trigger angle of the inverter; theta is the phase angle of the ac side voltage eac of the inverter.
2. The method of claim 1, wherein the performing a first iterative power flow calculation based on the obtained parameters of the dc transmission system components comprises:
calculating direct current power according to the obtained alternating current-direct current division point bus and direct current system parameters;
and (3) bringing the direct-current power into an alternating-current network to perform iterative power flow calculation to obtain the voltage of the alternating-current and direct-current division point bus, and obtaining the per-unit transformation ratio of the transformation current until power flow is converged.
3. The method as claimed in claim 2, wherein the step of obtaining the per-unit transformation ratio of the converter transformer when the power flow converges comprises the steps of:
correcting the per-unit transformation ratio of the transformation current according to the bus voltage of the alternating current-direct current division point; as shown in the following formula:
n id ＝U' o1 /U o2r /K
wherein n is id The per unit transformation ratio of the rectified rectifier side converter transformer is corrected; u' o1 Actual tap voltage after the first iteration load flow calculation is carried out; u shape o2r Rated voltage for the converter transformer valve side; k is the number of single-station unipolar six-pulse converters corresponding to the direct-current engineering;
actual tap voltage U 'after first iteration power flow calculation' o1 Calculated as follows:
U' o1 ＝U o1r +(Tap pos -Tap posr )*Tap step
wherein, U o1r A nominal voltage corresponding to a tap position in the nominal tap information; tap pos And Tap posr Respectively the current tap position and the main tap position of the converter transformer; tap step For the division of the tap adjustment, it is calculated as follows:
wherein, U o1 For the converter transformer primary side tap voltage, the following formula is calculated:
U ο1 ＝n i U ο2r K
wherein n is i And the per unit transformation ratio of the converter transformer in the iterative calculation is calculated.
4. The method as claimed in claim 1, wherein the step of correcting the per-unit transformation ratio of the transformed flow based on the first iterative power flow calculation result and then performing the second iterative power flow calculation includes:
calculating direct-current power based on the corrected per-unit transformation ratio, the alternating-current and direct-current division point bus voltage and the direct-current coefficient parameters;
injecting the direct current power into an alternating current network, solving alternating current power flow, and obtaining an improved value of the bus voltage of the alternating current-direct current division point;
and judging whether the alternating current power flow is converged, and if not, repeating the two steps until the alternating current power flow is converged.
5. The method for calculating an initial value for electromagnetic transient simulation as claimed in claim 1, wherein said calculating the phase angle of the ac side voltage eac of the converter according to the connection of said converter transformer comprises:
when the connection method of the converter transformer is Y-delta-1, the voltage phase angle of the network side line of the converter transformer is calculated according to the following formula:
θ＝A*180°/π-60°；
when the connection method of the converter transformer is Y-Y-0, the voltage phase angle of the network side line of the converter transformer is calculated according to the following formula
θ＝A*180°/π-30°；
Wherein, theta is a phase angle of the alternating-current side voltage eac of the converter; a is the voltage phase angle of the grid side line of the converter transformer.
6. The method according to claim 1, wherein the conduction state of each converter valve arm at the initial dc operation is determined according to the phase angle of the ac side voltage eac of the converter, the rectifier triggering lag angle, and the inverter triggering lead angle, wherein the rectifier triggering lag angle is calculated according to the following formula:
α＝ang0(ii)*180°/π
where α is the rectifier trigger lag angle, and ang0 (ii) is the initial value of the rectifier ii trigger lag angle;
the inverter trigger advance angle is calculated according to the following formula:
β＝ang0'(ii)*180°/π
where β is an inverter over-firing angle, and ang0' (ii) is an initial value of the inverter ii over-firing angle.
7. The method of claim 1, further comprising:
and according to the per-unit transformation ratio of the converter transformer, the direct-current trigger angle, the direct-current voltage, the state information of the direct current and the conduction state of each converter valve arm during the initial operation of the direct current, enabling the direct current circuit to be equivalent to a small-resistance circuit, and completing the initialization of the direct current circuit.
8. A computing system for providing initial values for electromagnetic transient simulation, comprising:
the first calculation module is used for performing first iteration power flow calculation based on the acquired direct current transmission system element parameters;
the second calculation module is used for correcting the per unit transformation ratio of the transformation flow based on the first iteration flow calculation result and then performing second iteration flow calculation;
the control module is used for determining the conduction state of each converter valve arm when the alternating current-direct current transmission system initially operates according to the second iteration load flow calculation result;
the determining the conduction state of each converter valve arm when the alternating current-direct current transmission system initially operates according to the second iteration load flow calculation result comprises the following steps:
obtaining the per-unit transformation ratio of the transformation current, the direct current trigger angle, the direct current voltage and the state information of the direct current according to the second iteration load flow calculation result;
calculating the phase angle of the AC side voltage eac of the converter according to the connection method of the converter transformer;
determining the conduction state of each converter valve arm in the initial direct current operation according to the phase angle of the alternating current side voltage eac of the converter, the trigger lag angle of the rectifier, the trigger lead angle of the inverter and the connection method of the converter transformer;
the determining of the conduction state of each converter valve arm during initial direct current operation according to the phase angle of the alternating-current side voltage eac of the converter, the trigger lag angle of the rectifier, the trigger lead angle of the inverter and the connection method of the converter transformer comprises the following steps:
if α -150 ° < θ ≦ α -90 °, S (ii) = [0, 1];
if α -90 ° < θ ≦ α -30 °, S (ii) = [1,0, 1];
if α -30 ° < θ ≦ α +30 °, S (ii) = [1, 0];
if α +30 ° < θ ≦ α +90 °, S (ii) = [0,1, 0];
if 0 ° < α ≦ 30 ° and α +90 ° < θ ≦ α +150 °, S (ii) = [0,1, 0];
if 30 ° < α <90 ° and α +90 ° < θ ≦ 180 °, S (ii) = [0,1, 0];
if 30 ° < α <90 ° and-180 ° < θ ≦ α -210 °, S (ii) = [0,1, 0];
if 0 ° < α <30 ° and-180 ° < θ ≦ α -150 °, S (ii) = [0,1, 0];
if 0 ° < α <30 ° and α +150 ° < θ ≦ 180 °, S (ii) = [0,1, 0];
if 30 ° < α <90 ° and α -210 ° < θ ≦ α -150 °, S (ii) = [0,1, 0];
if 90-beta < theta.ltoreq.150-beta, S (ii) = [1,0, 1];
if 30 ° - β < θ ≦ 90 ° - β, then S (ii) = [0, 1];
if-30 ° - β < θ ≦ 30 ° - β, then S (ii) = [0,1, 0];
if-90 ° - β < θ ≦ -30 ° - β, then S (ii) = [0,1, 0];
s (ii) = [0,1, 0] if 0 ° < β ≦ 30 ° and-150 ° - β < θ ≦ -90 ° - β;
s (ii) = [0,1, 0] if 30 ° < β <90 ° and-180 ° < θ ≦ -90 ° - β;
s (ii) = [0,1, 0] if 30 ° < β <90 ° and 210 ° - β < θ ≦ 180 °;
s (ii) = [1, 0] if 0 ° < β <30 ° and-180 ° < θ ≦ -150 ° - β;
s (ii) = [1, 0] if 0 ° < β <30 ° and 150 ° - β < θ ≦ 180 °;
(iii) S (ii) = [1, 0] if 30 ° < β <90 ° and 150 ° < β < θ < 210 ° - β;
s (ii) is a switching vector of the conducting state of each converter valve arm when the direct current transmission system initially operates; alpha is the trigger lag angle of the rectifier; beta is the trigger crossing angle of the inverter; theta is the phase angle of the ac side voltage eac of the inverter.
9. The computing system for providing initial values for electromagnetic transient simulation of claim 8, wherein said first computing module comprises:
the power calculation submodule is used for calculating direct-current power according to the obtained alternating-current and direct-current division point bus and the direct-current system parameters;
and the converter transformer per unit transformation ratio calculation submodule is used for bringing the direct-current power into the alternating-current network to carry out iterative power flow calculation to obtain the voltage of the alternating-current and direct-current division point bus until power flow is converged, and obtaining the converter transformer per unit transformation ratio.
10. The computing system for providing initial values for electromagnetic transient simulation of claim 9, wherein said per-unit transformation ratio of transformation flow is calculated as follows:
n id ＝U' o1 /U o2r /K
wherein n is id The per unit transformation ratio of the rectifier side converter transformer is corrected; u' o1 Calculating the actual tap voltage for the first iteration load flow; u shape o2r Rated voltage for the converter transformer valve side; k is the number of single-station unipolar six-pulse current converters corresponding to the direct-current engineering;
actual tap voltage U 'after first iteration power flow calculation' o1 Calculated as follows:
U' o1 ＝U o1r +(Tap pos -Tap posr )*Tap step
wherein, U o1r A nominal voltage corresponding to a tap position in the nominal tap information; tap pos And Tap posr Respectively the current tap position and the main tap position of the converter transformer; tap step For the division of the tap adjustment, the following is calculated:
wherein, U o1 For the converter transformer primary side tap voltage, the following formula is calculated:
U ο1 ＝n i U ο2r K
wherein n is i And the per-unit transformation ratio of the converter transformer in the iterative calculation is obtained.
11. The computing system for providing initial values for electromagnetic transient simulation of claim 8, wherein the second computing module comprises:
the direct current power calculation submodule: the DC power calculating unit is used for calculating DC power based on the corrected per unit transformation ratio, the AC/DC division point bus voltage and the DC coefficient parameter;
the load flow alternating current calculation submodule: the direct current power is injected into an alternating current network, alternating current power flow is solved, and an improved value of the bus voltage of the alternating current-direct current division point is obtained;
a judgment submodule: and determining the conduction state of each converter valve arm according to the second iteration load flow calculation result.
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